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Neidon
Neidon is an ice giant and the ninth planet of the Kerbol system. It is the third planet added in the Outer Planets Mod and is the Neptune analog for Kerbal Space Program. The planet is an attractive target to visit because of the deep blue and purple colors, however its distance makes it a difficult place to visit. Neidon also has two moons: Thatmo, and Nissee.. It also has a procedural system of asteroids if Custom Asteroids is installed. As with the other gas giants, it is not possible to land on Neidon - instead, the craft is simply destroyed. Neidon's great distance from Kerbol reduces solar panel output to under 0.11% of that at Kerbin, so bringing extra solar panels or an alternative power source (e.g. RTGs) for missions to Neidon and its moons is recommended. In-Game Description Atmosphere Neidon has a very cold, dense atmosphere that extends to an altitude of 260,000 meters and has an average molecular mass of 2.8 g/mol. This indicates a composition of mostly hydrogen (80%) and helium (19%), and a small amount of methane may contribute to the color. The upper atmosphere also has traces of hydrocarbons, carbon monoxide, and carbon dioxide. Like all other atmospheres in the game, Neidon's atmosphere fades exponentially as altitude increases. The scale height varies with altitude. The pressure-altitude profile is globally constant and independent of temperature. The following table gives the atmospheric pressure at various altitudes above the datum level. Judging by density and planet models, it's interesting to note that the atmosphere in game is only the outer layer. At sea-level the atmosphere of a realistic planet would start to gradually become liquid until it reached the icy mantle. This is also true for Urlum. Temperatures and Atmospheric Layers There appears to be several layers in Neidon's atmosphere - a Troposphere, where temperatures decrease with altitude, and a Stratosphere, where temperatures increase with altitude. The boundary between the troposphere and stratosphere is called the Tropopause, and occurs at an altitude of 25 km. There is also a Thermosphere which begins around 100 km and extends out to 160 km. Atmospheric flight Aerobraking into Neidon's orbit from a high-speed interplanetary intercept is possible but it is very difficult to achieve due to rapid and often destructive aerodynamic heating. A successful aerocapture requires a properly designed spacecraft, with a large ablator mass and a low ballistic coefficient, and precise periapsis targeting. The required periapsis altitude depends on the spacecraft's drag characteristics and its approach velocity. The margins for error are extremely small. You could also use parachutes in Neidon's atmosphere to slow your spacecraft down. Composition From the average density of the planet, it's possible to estimate models for its composition. One model suggests a solid core - likely iron (radius of 128.7 km) - surrounded by a mantle made of ices (water, ammonia, and methane with a radius of 645.3 km). The outer atmospheric layer begins to liquefy and harden to pressures that destroy any spacecraft. From the outer layer to the ice mantle could be 1,372.8 km. The deep purple and blue color could be due to methane in the atmosphere, which absorbs red light. Magnetosphere There is an extremely tilted magnetic field that indicates a magnetosphere that may be formed by convective fluids in the icy mantle or lower atmospheric regions, similar to Urlum. Possible Weather With certain graphical modifications installed, Neidon has rotating clouds. By observing the rotation of these clouds, wind speeds can be estimated to vary between 325 to 600 m/s, the fastest wind speeds in the game. Natural Satellites Neidon only has two natural satellites, each with a very inclined orbit: * Thatmo, an icy moon, has a very thin atmosphere and a retrograde orbit. * Nissee, a rocky moon, has a highly inclined and eccentric orbit. Synchronous Orbits around any of the Neidonean moons are impossible, as they all lie outside the Sphere of Influence of the moons, as is common with tidally locked bodies. Biomes Neidon has a total of eight (atmosphere and space-only) biomes. Biome list Reference frames Category:Celestials Category:Planets Category:OuterPlanetsMod